1. Field of the Invention
The present invention relates generally to fuel vapor emission control for internal combustion engines. More particularly, the present invention relates fuel tank fuel vapor emission control for internal combustion engines.
2. Description of the Related Art
Modern transportation vehicles which employ a liquid fuel conventionally also employ for storage of the liquid fuel a fuel tank. Similarly, since most liquid fuels are highly volatile, such a fuel tank typically contains in addition to the liquid fuel a fuel vapor. A concentration of fuel in the fuel vapor within the fuel tank is generally related to a temperature of the liquid fuel within the fuel tank and a temperature of the fuel vapor within the fuel tank.
While a fuel vapor within a fuel tank does not typically impair operation of a transportation vehicle which is powered by an engine which employs a liquid fuel extracted from the fuel tank, upon refueling of the fuel tank with additional liquid fuel the fuel vapor must of necessity be displaced. For environmental protection purposes and for economic reasons, it is desirable for such displaced fuel vapor not to be released into the atmosphere.
Various apparatus, systems and methods have been disclosed within the art of fuel system design for attenuating, upon refueling of a fuel tank, release of a fuel vapor into the atmosphere. Well known in this regard are fuel system designs which incorporate the use of carbon filled fuel vapor retention canisters for cyclical absorptive capture and desorptive controlled release of a fuel vapor displaced incident to refueling of a fuel tank. Examples of such fuel system designs are disclosed within U.S. Pat. No. 4,829,968, U.S. Pat. No. 5,014,742, U.S. Pat. No. 5,054,528, U.S. Pat. No. 5,239,824, U.S. Pat. No. 5,275,145, U.S. Pat. No. 5,305,724, U.S. Pat. No. 5,456,238, U.S. Pat. No. 5,826,565, U.S. Pat. No. 5,915,364 and U.S. Pat. No. 5,934,260, all of which are incorporated herein fully by reference.
While any of the foregoing disclosed fuel system designs provides upon refueling of a fuel tank with a liquid fuel an attenuated displaced fuel vapor release into the atmosphere, such desirable result is often achieved only with complicated piping and valving schemes, or often achieved only while still encountering fuel vapor canister breathing or dissipation losses with respect to a carbon filled fuel vapor retention canister which is either open to the atmosphere or vented to the atmosphere.
There thus exists within the art of fuel system design a continuing need for comparatively simple apparatus, systems and methods for attenuating upon refueling of a fuel tank release of a displaced fuel vapor into the atmosphere.
It is towards that object that the present invention is directed.